It is known in the iron and steel industry to use iron-based pipes, or lances, to purge slag material from ladles of molten iron or steel by forcing oxygen into the molten material. Inherent in this process, however, is the problem of degradation and corrosion of the iron-based pipes as a result of the harsh operating environment. For instance, the pipes are partially submerged in molten iron or steel, the temperature of which may be as high as 3200.degree. F. Further, thermal shock and other stresses are encountered, as well as the action of the slag material and molten metal itself which proves to be corrosive.
Consequently, the average life of the typical iron-based pipe used for this procedure is very limited. Others have attempted to correct this problem by coating the pipe with ceramic material. This, however, has drawbacks of its own.
It has now been discovered that a coating of the type described herein can be applied and bonded to iron-based pipe to be used in iron and steel working resulting in the increased life of the pipe. The subject invention concerns a thermally stable coating, for iron-based pipes used in the iron and steel industry, which increases the operable life of the pipes which must function in extremely harsh conditions with respect to high temperature, thermal shock and other various physical, mechanical and chemical stresses.
The coating includes fine and coarse grade silica, clay, binder material, and other various components which form a vitrified, continuous shell over all exposed surfaces of an iron-based pipe, enhancing the life of the pipe by up to as much as seven times that of an uncoated pipe used in the same application.